systemctl: load unit if needed in "systemctl is-active"

Previously, we'd explicitly use "GetUnit()" on the server side to
convert a unit name into a bus path, as that function will return an
error if the unit is not currently loaded. If we'd convert the path on
the client side, and access the unit this way directly the unit would be
loaded automatically in the background.

The old logic was done in order to minimize the effect of "is-active" on
the system, i.e. that a monoitoring command does not itself alter the
state of the system.

however, this is problematic as this can lead to confusing results if
the queried unit name is an alias that currently is not loaded: we'd
claim the unit wasn't active even though this isn't strictly true: the
unit the name is an alias for might be.

Hence, let's simplify the code, and accept that we might end up loading
a unit briefly here, and let's make "systemctl is-active" skip the
GetUnit() thing and calculate the unit path right away.

Fixes: #7875

1 files changed, 16 insertions, 39 deletions

diff --git a/src/systemctl/systemctl.c b/src/systemctl/systemctl.c
index 30077d319d..5732d88a17 100644
--- a/src/systemctl/systemctl.c
+++ b/src/systemctl/systemctl.c
@@ -2650,55 +2650,32 @@ static int unit_find_paths(
 
 static int get_state_one_unit(sd_bus *bus, const char *name, UnitActiveState *active_state) {
         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
-        _cleanup_(sd_bus_message_unrefp) sd_bus_message *reply = NULL;
-        _cleanup_free_ char *buf = NULL;
+        _cleanup_free_ char *buf = NULL, *path = NULL;
         UnitActiveState state;
-        const char *path;
         int r;
 
         assert(name);
         assert(active_state);
 
-        /* We don't use unit_dbus_path_from_name() directly since we don't want to load the unit unnecessarily, if it
-         * isn't loaded. */
-        r = sd_bus_call_method(
+        path = unit_dbus_path_from_name(name);
+        if (!path)
+                return log_oom();
+
+        r = sd_bus_get_property_string(
                         bus,
                         "org.freedesktop.systemd1",
-                        "/org/freedesktop/systemd1",
-                        "org.freedesktop.systemd1.Manager",
-                        "GetUnit",
+                        path,
+                        "org.freedesktop.systemd1.Unit",
+                        "ActiveState",
                         &error,
-                        &reply,
-                        "s", name);
-        if (r < 0) {
-                if (!sd_bus_error_has_name(&error,  BUS_ERROR_NO_SUCH_UNIT))
-                        return log_error_errno(r, "Failed to retrieve unit: %s", bus_error_message(&error, r));
-
-                /* The unit is currently not loaded, hence say it's "inactive", since all units that aren't loaded are
-                 * considered inactive. */
-                state = UNIT_INACTIVE;
-
-        } else {
-                r = sd_bus_message_read(reply, "o", &path);
-                if (r < 0)
-                        return bus_log_parse_error(r);
-
-                r = sd_bus_get_property_string(
-                                bus,
-                                "org.freedesktop.systemd1",
-                                path,
-                                "org.freedesktop.systemd1.Unit",
-                                "ActiveState",
-                                &error,
-                                &buf);
-                if (r < 0)
-                        return log_error_errno(r, "Failed to retrieve unit state: %s", bus_error_message(&error, r));
+                        &buf);
+        if (r < 0)
+                return log_error_errno(r, "Failed to retrieve unit state: %s", bus_error_message(&error, r));
 
-                state = unit_active_state_from_string(buf);
-                if (state == _UNIT_ACTIVE_STATE_INVALID) {
-                        log_error("Invalid unit state '%s' for: %s", buf, name);
-                        return -EINVAL;
-                }
+        state = unit_active_state_from_string(buf);
+        if (state == _UNIT_ACTIVE_STATE_INVALID) {
+                log_error("Invalid unit state '%s' for: %s", buf, name);
+                return -EINVAL;
         }
 
         *active_state = state;